On Fri, Apr 07, 2023 at 08:09:23PM +0300, Dmitry Baryshkov wrote: > On 07/04/2023 19:48, Bjorn Andersson wrote: > > On Wed, Jan 18, 2023 at 08:47:53PM +0200, Dmitry Baryshkov wrote: > > > 18 января 2023 г. 19:32:42 GMT+02:00, Bjorn Andersson <andersson@xxxxxxxxxx> пишет: > > > > On Wed, Jan 18, 2023 at 10:20:48AM +0200, Dmitry Baryshkov wrote: > > > > > While we are testing the DB845c working in dual DSI mode (which is > > > > > required for the 4k support), create a separate device tree using this > > > > > configuration. > > > > > > > > > > > > > I don't think it's right to change the DTB on your device depending on > > > > your TV's ability to do 4k or not... > > > > > > > > I ran into this problem when playing around with 4k-support on the RB3 > > > > as well a while back. I was not able to figure out a way to run the > > > > lt9611 off two inputs for the lower resolutions and ended never posted > > > > anything because I couldn't come up with any good solution. > > > > > > > > > This is implemented with the latest lt9611 patchset, referenced in the patch annotation. > > > > > > I posted this as an RFC with the separate dts to let people test dual DSI, DPU wide planes, etc. and to compare that with plain old single link DSI/lt9611. > > > > > > > > > > > > > > > Would it be possible somehow to describe the two ports in DT, but have > > > > the display driver use one or both depending on the number of inputs > > > > needed by the lt9611? > > > > > > This would be very problemsome. Even switching the number of lanes > > > goes against the standard and is not supported by Linux kernel. > > > Supporting switching the host off and on would be a real troublle. > > > > > > > Does this imply that switching resolution in runtime is not possible for > > any of these DSI->HDMI/DP/eDP bridges? > > > > The immediate worry is that we need 4k and non-4k variants of every > > mezzanine (unless we start doing overlays). But beyond that I still > > don't like the fact that you need to change firmware depending on which > > monitor/TV you're going to connect the board to. (And with the current > > boot.img-based design, this is overly cumbersome) > No. With the latest lt9611 driver and with the current msm/msm-next it > should not be necessary to have a separate dtsi. I submitted this patch as > an RFC to let people compare 2xDSI vs single-link cases. Currently I'm happy > with the way it works, so I can probably send this as a patch to main > sdm845-db845c.dtb. > > As a background info: > - lt9611 driver can utilize either one or two DSI links > - drm/msm can output 4k over two DSI links in bonded mode. > - drm/msm will still utilize two DSI links for smaller resolutions > (switching between single and bonded DSI modes doesn't seem practical). > - If just one DSI link is supplied, 1080p is the maximum resolution that can > be supported. > Sorry, I missed your reply earlier. If we can run the lower resolutions off two bonded DSI I think we should make that the default configuration - it's just that when I tried it a few years ago I had problems getting a working output... But much has changed since then. There is a dip switch to allow one of the DSI links to be passed onto one of the HS-connectors, but for anyone to use that they would need a mezzaine dts anyways, so they can unbond the DSIs there. Regards, Bjorn
